Paul Hepperly

Environmental, Energetic, and Economic Comparisons of Organic and Conventional Farming Systems

Abstract Various organic technologies have been utilized for about 6000 years to make agriculture sustainable while conserving soil, water, energy, and biological resources. Among the benefits of organic technologies are higher soil organic matter and nitrogen, lower fossil energy inputs, yields similar to those of conventional systems, and conservation of soil moisture and water resources (especially advantageous under drought conditions). Conventional agriculture can be made more sustainable and ecologically sound by adopting some traditional organic farming technologies.

Compost, Manure and Synthetic Fertilizer Influences Crop Yields, Soil Properties, Nitrate Leaching and Crop Nutrient Content

From 1993 to 2001, a maize-vegetable-wheat rotation was compared using either 1) composts, 2) manure, or 3) synthetic fertilizer for nitrogen nutrient input. From 1993 to 1998, red clover (Trifolium pratense L.) and crimson clover (Trifolium incarnatum L.) were used as an annual winter legume cover crop prior to maize production. From 1999 to 2001, hairy vetch (Vicia villosa Roth.) served as the legume green manure nitrogen (N) source for maize. In this rotation, wheat depended entirely on residual N that remained in the soil after maize and vegetable (pepper and potato) production. Vegetables received either compost, manure, or fertilizer N inputs. Raw dairy manure stimulated the highest overall maize yields of 7,395 kg/ha (approximately 140 bushels per acre). This exceeded the Berks County mean yield of about 107 bushels per acre from 1994 to 2001. When hairy vetch replaced clover as the winter green manure cover crop, maize yields rose in three of the four treatments (approximately 500-1,300 kg/ha, or 10-24 bu/a). Hairy vetch cover cropping also resulted in a 9-25 % increase in wheat yields in the compost treatments compared to clover cover cropping. Hairy vetch cover crops increased both maize and wheat grain protein contents about 16 to 20% compared to the clover cover crop. Compost was superior to conventional synthetic fertilizer and raw dairy manure in 1) building soil nutrient levels, 2) providing residual nutrient support to wheat production, and 3) reducing nutrient losses to ground and surface waters. After 9 years, soil carbon (C) and soil N remained unchanged or declined slightly in the synthetic fertilizer treatment, but increased with use of compost amendments by 16-27% for C and by 13-16% for N. However, with hairy vetch cover crops, N leaching increased 4 times when compared to clover cover crops. September was the highest month for nitrate leaching, combining high rainfall with a lack of active cash crop or cover crop growth to use residual N. Broiler litter leaf compost (BLLC) showed the lowest nitrate leaching of all the nutrient amendments tested (P= 0.05).

Inoculation with Arbuscular Mycorrhizal Fungi Increases the Yield of Potatoes in a High P Soil

ABSTRACT Arbuscular mycorrhizal (AM) fungi are potentially important tools in agricultural systems that reduce or eliminate chemical inputs common in modem agriculture. We tested the response of potato (Solanum tuberosum L. cv. Superior) to inoculation with AM fungi in a field with very high available P (375 μg g−l soil) in two growing seasons. Inoculation treatments included a commercially available inoculum containing Glomus intraradices, mixed species inocula produced on-farm in mixtures of compost and vermiculite, and a control treatment consisting of a freshly prepared compost and vermiculite mixture. In addition, two farming systems were imposed: conventional chemical fertilizers or dairy manure composted with leaves were applied to meet recommended nutrient requirements. Yields of tubers on a fresh weight basis in the first year were significantly increased by AM fungus inoculum, 33% under conventional fertilizer application and 45% with compost addition vs. controls in each system. The response to inoculation the second year was less; however yields of inoculated plants were 10 to 20% greater than controls. There was a significant positive treatment effect of inoculation upon production of larger sized potatoes in the second year. Neither year saw a marked difference in yield response among AM fungus inocula. These results demonstrate the potential yield benefits of inoculation of potatoes with AM fungi produced on the farm.

On-farm production of inoculum of indigenous arbuscular mycorrhizal fungi and assessment of diluents of compost for inoculum production.

On-farm production of arbuscular mycorrhizal [AM] fungus inoculum can be employed to make the benefits of the symbiosis more available to vegetable farmers. Experiments were conducted to modify an existing method for the production of inoculum in temperate climates to make it more readily adoptable by farmers. Perlite, vermiculite, and peat based potting media were tested as diluents of yard clippings compost for the media in which the inoculum was produced using bahiagrass (Paspalum notatum Flugge) as host plant. All produced satisfactory concentrations of AM fungus propagules, though vermiculite proved to be better than potting media (89 vs. 25 propagules cm(-3), respectively). Two methods were tested for the growth of AM fungi indigenous to the farm: (1) adding field soil into the vermiculite and compost mixture and (2) pre-colonizing the bahiagrass seedlings in media inoculated with field soil prior to transplant into that mixture. Adding 100 cm(3) of field soil to the compost and vermiculite produced 465 compared to 137 propagules cm(-3) for the pre-colonization method. The greater flexibility these modifications give will make it easier for farmers to produce inoculum of AM fungi on-the-farm.

Choosing a Mixture Ratio for the On-Farm Production of AM Fungus Inoculum In Mixtures of Compost and Vermiculite

Arbuscular mycorrhizal [AM] fungi are potentially important tools in sustainable agriculture due to their roles in crop nutrient uptake, disease resistance, and water relations and in stabilizing soil aggregates. Inocula of these fungi can be effectively produced on-farm in mixtures of compost and vermiculite with a suitable plant host, such as bahiagrass (Paspalum notatum Flugge). Success of this method, however, depends upon utilizing the optimal compost and vermiculite mixture ratio. Experiments were conducted over two years utilizing a complete factorial design with three composts, four mixture ratios, and three AM fungi with the objective of producing regression equations to predict optimal mixture ratios using routine measures of compost nutrient analyses as independent variables. Growth of colonized P. notatum in yard clippings and dairy manure + leaf composts; which were high in N, low in P, with moderate K levels; produced more spores of AM fungi at mixture ratios of 1:2 to 1:4 [v/v compost: vermiculite] relative to higher dilutions. Dilution ratios of 1:19 and 1:49 were best for controlled microbial compost, which was high in P, low in N, and moderately high in K. Simple equations were developed which predict the optimal fraction of compost in the mixture for each of the three AM fungi studied (Glomus intraradices, Glomus mosseae, and Gigaspora rosea). Percent N, P, and K and N:P ratio were the significant independent variables. These equations allow a farmer to choose a mixture ratio for the on-farm propagation of AM fungi knowing only the nutrient analysis of the compost to be used.